The present invention relates to a technology of producing a lead frame and a technology of configuring a semiconductor device using the lead frame and, in particular, a technology effectively solving problems caused by camber of the lead frame when a dam member is employed in place of a dam bar.
Conventionally, a lead frame includes a dam bar fabricated with the same material together with the lead frame in a monoblock configuration. The dam bar prevents encapsulation resin from flowing toward the outer lead side in the transfer mold process. Since the dam bar is integrally formed in the lead frame, to achieve a cutoff process of the dam bar, it is necessary to conduct a cutting process using a metal mold.
However, recently, due to increasing tendency of capacity of semiconductor devices, the number of pins of a semiconductor device package becomes greater, which necessitates a lead frame of a finer pitch construction having a lead pitch of 0.3 mm to 0.5 mm. This leads to a technological problem that it is difficult to conduct the cutting process of the dam bar by use of a metal mold. Even if the process is conducted, the production cost will be considerably increased. For this problem, to remove the cutoff process using a metal mold, there have been proposed methods of creating a dam bar in which, in place of the forming of the dam bar in the monoblock structure, an insulating tape and a resin are used as members of the dam. Reference is to be made to, for example, the JP-A-58-28841, JP-A-2-122660, JP-A-310955, and JP-A-4-91464.
According to the methods above, the dam bar can be easily formed in a multi-pin lead frame and can be removed after the molding process in a simple process using, for example, an organic solvent. In addition, since the dam bar is fabricated with an insulating material, the process of removing the dam bar may possibly be dispensed with in some cases.